Data from: Testing the effects of ant invasions on non-ant arthropods with high-resolution taxonomic data

Invasions give rise to a wide range of ecological effects. Many invasions
proceed without noticeable impacts on the resident biota, whereas others
shift species composition and even alter ecosystem function. Ant invasions
generate a broad spectrum of ecological effects, but controversy surrounds
the extent of these impacts, especially with regard to how other
arthropods are affected. This uncertainty in part results from the
widespread use of low-resolution taxonomic data, which can mask the
presence of other introduced species and make it difficult to isolate the
effects of ant invasions on native species. Here, we use high-resolution
taxonomic data to examine the effects of Argentine ant invasions on
arthropods on Santa Cruz Island, California. We sampled arthropods in
eight pairs of invaded and uninvaded plots and then collaborated with
taxonomic experts to identify taxa in four focal groups: spiders, bark
lice, beetles, and ants. Spiders, bark lice, and beetles made up ~40% of
the 9868 non-ant arthropod individuals sampled; the majority of focal
group arthropods were putatively native taxa. Although our results
indicate strong negative effects of the Argentine ant on native ants, as
is well documented, invaded and uninvaded plots did not differ with
respect to the richness, abundance, or species composition of spiders,
bark lice, and beetles. One common, introduced species of bark louse was
more common in uninvaded plots than in invaded plots, and including this
species into our analyses changed the relationship between bark louse
richness vs. L. humile abundance from no relationship to a significant
negative relationship. This case illustrates how failure to differentiate
native and introduced taxa can lead to erroneous conclusions about the
effects of ant invasions. Our results caution against unqualified
assertions about the effects of ant invasions on non-ant arthropods, and
more generally demonstrate that accurate assessments of invasion impacts
depend on adequate information about species identity.